Researching the Circulatory System also called the Cardiovascular System.
List the organs found in this system
Explain the functions of this system
What other systems of the body does the circulatory system interact with?

b. the carbon cycle ensures living things have a source of hydrogen

well, since there is no answer choices, i will give an answer on how it works : )

the two objects are placed together. energy will always be transferred from the hotter object to the cooler object until they are equal. hope this is close to one of the answer choices : )